1. Field of the Invention
The present invention relates generally to radiography systems and more specifically to a combination modular computed and direct radiography system and method.
2. Background of the Invention
Computed radiography (“CR”) systems generate a digital image of an x-ray by scanning an x-ray storage phosphor imaging plate that has been exposed to x-ray energy, usually while at least partially housed in a cassette. The re-useable imaging plate replaces the need for previously conventional x-ray film. The imaging plate is typically coated with photostimulable storage phosphors allowing it to store the energy received from the x-ray irradiation. The cassette encases the imaging plate and prevent exposure from ambient and other light sources
In a typical CR procedure, the desired object is exposed to x-rays from one perspective with the imaging plate generally positioned on the opposite side so as to capture those x-rays passing through the object. This results in a latent image being formed and stored on the imaging plate. Multiple plates may be used for multiple x-rays images of the desired object or person or for a larger x-ray image. After exposure by x-rays, the imaging plate is encased in its cassette and taken to a CR system for image processing.
The CR device creates an image by stimulating the storage phosphors within the imaging plate using a laser beam, typically with a wavelength from between 600 nm to 800 nm, driven across the irradiated area of the imaging plate. Point by point or line by line stimulation by the laser causes the imaging plate to release light in direct proportion to the latent energy previously stored as a result of the x-ray irradiation hitting the surface of the phosphors. The light released by the imaging plate is captured by the CR scanning and optical system and converted into an electrical signal. This signal is then converted to digital data that can be manipulated and ultimately viewed on a monitor, printed, transferred to remote systems for further analysis, storage or computations.
Various companies produce CR systems with each using slightly different means for exciting the phosphor plate and capturing the released light energy as well as handling the imaging plate. The advantages and drawbacks of these CR systems relative to other radiography systems are well known. Commonly cited drawbacks include the need to typically handle the imaging plate within a cassette, the burden of moving the imaging plate cassette from the x-ray exposure position to the CR system and then scanning it to obtain the desired image. In addition to requiring additional handling, these efforts increase the time before an image is actually created by the CR system. Other cited drawbacks include the overall size of the system, cost and complexity of the devices, including the time and costs associated with repairing and maintenance.
Direct radiography (“DR”) systems are another form of x-ray imaging similar to CR systems in that they typically employ phosphor scintillation materials to generate an image. These systems, however, do not use cassettes containing imaging plates. In a typical DR system, the x-ray energy is directed through the desired object and onto a DR imaging plate assembly. The typical DR imaging plate utilizes phosphor scintillation material bonded to pixel sized sensors. X-ray energy hitting the phosphor layer generates energy that is sensed by each pixel sensor within the detector and sent directly to the DR system amplifications electronics for generation of the image or other data. In a DR system, no intermediate steps or processes are required to obtain the image data.
In addition to generally eliminating the burden and time required to move the imaging plate cassette from the x-ray position to the CR system, most DR systems also advantageously utilize a scaled imaging plate. Because the sealed plate does not need to maintain stored x-ray energy or be moved for processing, the risk of ambient light or other contaminants affecting the otherwise stored latent image is eliminated.
What is also needed is a single device that has the advantages of both CR and DR and that can be used in both applications.